Polyurethane polymers and compositions made using discrete carbon nanotubes

ABSTRACT

In various embodiments a urethane/MOLECULAR REBAR formulation comprising a specific composition is disclosed. The composition comprises a urethane polymer or prepolymer/discrete carbon nanotube formulation. Utility of the urethane/MOLECULAR REBAR composition includes improved foams and adhesives.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application claims priority to U.S. Provisional PatentApplication No. 61/669,109, filed Jul. 8, 2012, and titled “POLYURETHANEPOLYMERS AND COMPOSITIONS MADE USING DISCRETE CARBON NANOTUBE MOLECULARREBAR” as well as U.S. Provisional Patent Application No. 61/737,025,filed Dec. 13, 2012, and titled “POLYURETHANE POLYMERS AND COMPOSITIONSMADE USING DISCRETE CARBON NANOTUBE MOLECULAR REBAR”; and is related toU.S. Ser. No. 13/164,456 filed Jun. 20, 2011; U.S. Ser. No. 12/968,151filed Dec. 14, 2010; U.S. Ser. No. 13/140,029 filed Dec. 18, 2009; U.S.Ser. No. 61/500,561 filed Jun. 23, 2011; U.S. Ser. No. 61/500,560 filedJun. 23, 2011; and U.S. Ser. No. 61/638,454 filed Apr. 25, 2012; thedisclosures of which are incorporated herein by reference.

BACKGROUND

Carbon nanotubes in various forms have been disclosed. However,conventional carbon nanotubes, in the form of fibers or fibrils, are“clumped” together, making them less than ideal or even useful to theirfull potential, due to the entangled nature of the fibers. The presentinvention provides a method for separating these nanotubes intoindividual fibers and fibrils, and these separated “discrete”(un-entangled) carbon nanotube fibers are useful in many applications,including reinforcement of other materials. In an embodiment of thepresent invention, discrete carbon nanotube fibers are used in urethanepolymers and prepolymers, especially for making rigid and flexiblefoams, adhesives, sealants, coatings, and elastomers.

SUMMARY

One embodiment of the present invention is a composition comprising atleast one urethane based polymer or pre-polymer and at least a portionof discrete carbon nanotube MOLECULAR REBAR to form or polymerize into apolyurethane/MOLECULAR REBAR formulation.

Another embodiment is a composition comprising at least one urethanebased polymer or pre-polymer and at least a portion of discrete carbonnanotube molecular rebar, wherein the urethane polymer or pre-polymercomprises at least one polyol and/or at least one isocyanate, andwherein the discrete carbon nanotube molecular rebar is contacted withat least one of the polyol, the urethane polymer or pre-polymer.

Preferably the discrete carbon nanotube molecular rebar is contactedwith the polyol. The discrete carbon nanotubes can be contacted with thepolyol prior to, during and/or after polymerization. The discrete carbonnanotube molecular rebar can be contacted with the isocyanate prior to,during and/or after polymerization.

The isocyanate can comprise aromatic or aliphatic groups, preferablyhexamethylene diisocyanate, more preferably toluene diisocyanate or mostpreferably diphenylmethane diisocyanate.

The portion of discrete carbon nanotubes can be open ended, resultingfrom dissolving catalyst particles integral to the initially closedcarbon nanotubes.

The composition can further comprise at least one polymer other thanurethane polymer or prepolymer. The polymer can be selected from thegroup consisting of vinyl polymers, preferably poly(styrene-butadiene),partially or fully hydrogenated poly(styrene butadiene) containingcopolymers, functionalized poly(styrene butadiene) copolymers such ascarboxylated poly(styrene butadiene) and the like,poly(styrene-isoprene), poly(methacrylic acid), poly(acrylic acid),poly(vinylalcohols), and poly(vinylacetates), fluorinated polymers,preferably poly(vinylidine difluoride) and poly(vinylidene difluoride)copolymers, conductive polymers, preferably poly(acetylene),poly(phenylene), poly(pyrrole), and poly(acrylonitrile), polymersderived from natural sources, preferably alginates, polysaccharides,lignosulfonates, and cellulosic based materials, polyethers, polyesters,polyurethanes, and polyamides, either as graft, block or randomcopolymers, and mixtures thereof.

The carbon nanotubes can be further functionalized, preferablycomprising a molecule of mass greater than 50 g/mole and more preferablycomprising carboxylate, hydroxyl, ester, ether, or amide moieties, ormixtures thereof.

The discrete carbon nanotubes can have a residual metals level of lessthan about 4% by weight of the carbon nanotubes. The carbon nanotubefibers can comprise an oxidation content from about 1 weight percent toabout 15 weight percent. The discrete carbon nanotube fibers comprisefrom about 0.1 weight percent to about 90 weight percent, preferablyfrom about 0.5 to about 49 weight percent of the composition.

The composition can be in the form of free flowing particles.

The composition can comprise additional inorganic structures. Theadditional inorganic structures can comprise elements selected from thegroups two through fourteen of the Periodic Table of Elements,preferably wherein the elements are selected from the group consistingof silver, gold, silicon, vanadium, titanium, chromium, iron, manganese,tin, nickel, palladium, platinum, cobalt, aluminum, gallium, germanium,indium, antimony, copper and zinc, cadmium, mercury, or mixtures thereofincluding oxides and other derivatives. The additional inorganicstructures can also comprise non-fiber carbon structures, such ascomponents selected from the group consisting of carbon black, graphite,graphene, oxidized graphene, fullerenes and mixtures thereof.

Another embodiment of the invention is a foam comprising the inventiveformulations, wherein the foam at a given density has increasedrigidity, increased strength, improved ability to form foams, improvedcrush resistance, and improved static electricity transmission, comparedto a formulation in the absence of discrete carbon nanotube MOLECULARREBAR.

A further embodiment is an adhesive comprising the formulations, whereinthe adhesive has improved adhesion and cohesion and improved electricalproperties versus a comparison adhesive made with an absence of discretecarbon nanotube MOLECULAR REBAR.

A fourth embodiment is a cement comprising MOLECULAR REBAR, wherein thecement has improved crack resistance, preferably with improved adhesionto other materials placed in contact with the cement compared to thecement without MOLECULAR REBAR. The cement comprising MOLECULAR REBAR isespecially useful in the oil and gas drilling and processing industry,nuclear energy generation industry, mining and power generationindustries. Mortar comprising the cement of the inventive formulationsfor cement blocks and rocks resists cracking and crumbling which insurelonger life compared to a mortar without MOLECULAR REBAR.

Another embodiment is a process to form a composition comprisingpolyurethane/discrete carbon nanotube MOLECULAR REBAR formulationcomprising the steps of:

-   -   a) selecting discrete carbon nanotube fibers having an aspect        ratio of from 10 to 500,    -   b) selecting discrete carbon nanotube fibers having an oxidation        level from about 1 to about 15% by weight,    -   c) selecting discrete carbon nanotubes wherein at least a        portion of the tubes are open ended,    -   d) blending the discrete carbon nanotube fibers with a urethane        polymer or prepolymer to form a urethane/discrete carbon        nanotube carbon fiber mixture,    -   e) optionally polymerizing the urethane/fiber mixture with a        polyol and/or a isocyanate to form a polyurethane/molecular        rebar formulation,    -   f) optionally combining the urethane/discrete carbon fiber        nanotube mixture with additional inorganic structures, and    -   g) optionally agitating or sonicating, preferably sonicating,        the urethane/discrete carbon fiber nanotube mixture to a degree        sufficient to disperse the fibers.

BRIEF DESCRIPTION OF DRAWINGS

The following drawings form part of the present specification and areincluded to further demonstrate certain aspects of the presentinvention. The invention may be better understood by reference to one ormore of these drawings in combination with the detailed description ofspecific embodiments presented herein.

FIG. 1 shows a high magnification optical photograph of MOLECULAR REBAR1 (discrete carbon nanotubes) dispersed in polyethylene oxide. Thepolyethylene oxide has crystallized exhibiting well-known spherulites.The discrete carbon nanotubes of this invention are located essentiallyat the boundary of the crystalline-amorphous region and within theamorphous (non-crystalline fraction) as illustrated by the arrow 1 inthe figure. Arrow 2 shows the crystalline lamellar arm of thespherulite.

DETAILED DESCRIPTION

In the following description, certain details are set forth such asspecific quantities, sizes, etc. so as to provide a thoroughunderstanding of the present embodiments disclosed herein. However, itwill be evident to those of ordinary skill in the art that the presentdisclosure may be practiced without such specific details. In manycases, details concerning such considerations and the like have beenomitted inasmuch as such details are not necessary to obtain a completeunderstanding of the present disclosure and are within the skills ofpersons of ordinary skill in the relevant art.

While most of the terms used herein will be recognizable to those ofordinary skill in the art, it should be understood, however, that whennot explicitly defined, terms should be interpreted as adopting ameaning presently accepted by those of ordinary skill in the art. Incases where the construction of a term would render it meaningless oressentially meaningless, the definition should be taken from Webster'sDictionary, 3rd Edition, 2009. Definitions and/or interpretations shouldnot be incorporated from other patent applications, patents, orpublications, related or not, unless specifically stated in thisspecification.

The general term “polyurethane” is given to polymers prepared accordingto the diisocyanate-polyaddition principle with a basic building blockof a urethane linkage —NCO+HO—=>NI—CO—O—. They can incorporate a largevariety of other chemical moieties including, but not limited to, ether,ester and urea groups. These products can be named polyetherureas,polyureas, polyisocyanurates and polycarbodiimides and containquantities of urethane linkages as low as about 4% by number of alllinkages in the polymer. They can be made in the form of closed or opencell foams, coatings, fibers or solid films and sheets. The mechanicalproperties of the polyurethanes at 25° C. can range from rigid toflexible dependent on the amount of the “soft phase” i.e., moieties witha glass transition temperature less than 25° C. and the amount of “hardphase” i.e., moieties with a glass transition or a crystalline segmentmelting point higher than about 25° C.

Typical commercial diisocyanates are toluene diisocyanate (TDI),diphenylmethane (or methylene diphenyl) diisocyanate (MDI) andhexamethylene diisocyanate. Various isomers of these diisocyanates areavailable dependent on their method of manufacture. Typical soft phasecomponents are i.e., polymers such as hydroxyl terminated polyetherswith, for example molecular weight number average values up to 8000g/mole. Diols, triols such as ethylene glycol and trimethylolpropane andpolyfunctional hydroxyls such as penterythritol (or collectively,polyols) can be employed as chain extenders or crosslinkers with thediisocyanates. Diamines, triamines and polyamines can also be employedas more reactive entities than hydroxyls towards the diisocyanates.

Polyurethanes can also be made as water-borne or solvent-borne systemsfor coatings or adhesives. Additives such as, but not limited to, flameretardants, fillers such as mineral or glass, mold release agents,pigments, biocides, blocking agents, foam stabilizers and antioxidants,can be added to further provide desired features. Foam blowing agentsinclude low boiling point fluids such as, but not limited to, carbondioxide, water and fluorocarbons.

During the process of making discrete or exfoliated carbon nanotubes(which can be single, double and multiwall configurations), thenanotubes are cut into segments with at least one open end and residualcatalyst particles that are interior to the carbon nanotubes as receivedfrom the manufacturer are removed. This cutting of the tubes helps withexfoliation. The cutting of the tubes reduces the length of the tubesinto carbon nanotube segments that are defined here as MOLECULAR REBAR.Proper selection of the carbon nanotube feed stock related to catalystparticle type and distribution in the carbon nanotubes allows morecontrol over the resulting individual tube lengths and overall tubelength distribution. A preferred selection is where the internalcatalyst sites are evenly spaced and where the catalyst is mostefficient. The preferred aspect ratio (length to diameter ratio) isgreater than about 25 and less than about 100 for a balance of viscosityand mechanical performance. The selection can be evaluated usingelectron microscopy and determination of the discrete or exfoliated tubedistribution.

MOLECULAR REBAR has oxidized species on the surface. Oxidized speciesinclude but not limited to carboxylates, hydroxyls and lactones. Theoxidized species can react advantageously with species within theurethane such as an isocyanate, hydroxyl or amine group. This reactionincreases the bonding strength between the MOLECULAR REBAR and thematrix. The MOLECULAR REBAR may further comprise a dispersing agent,adhesively or covalently bonded to the MOLECULAR REBAR surface. As aresult of the aforementioned, MOLECULAR REBAR gives advantageousmechanical and transport properties when added to other materialscompared to materials with no MOLECULAR REBAR.

The discrete oxidized carbon nanotubes (or DCNT), alternatively termedexfoliated carbon nanotubes, of the present disclosure take advantage ofproperties such as electrical, thermal, physical and ion transport,offered by individual carbon nanotubes that are not apparent when thecarbon nanotubes are aggregated into bundles.

Discrete oxidized carbon nanotubes, alternatively termed exfoliatedcarbon nanotubes, are obtained from as-made bundled carbon nanotubes bymethods such as oxidation using a combination of concentrated sulfuricand nitric acids. However, the techniques disclosed in U.S. Ser. Nos.13/164,456 and 13/140,029, the disclosures of which are incorporatedherein by reference, are particularly useful in producing the discretecarbon nanotubes used in this invention. The bundled carbon nanotubescan be made from any known means such as, for example, chemical vapordeposition, laser ablation, and high pressure carbon monoxide synthesis.The bundled carbon nanotubes can be present in a variety of formsincluding, for example, soot, powder, fibers, and bucky paper.Furthermore, the bundled carbon nanotubes may be of any length,diameter, or chirality. Carbon nanotubes may be metallic, semi-metallic,semi-conducting, or non-metallic based on their chirality and number ofwalls. The discrete oxidized carbon nanotubes may include, for example,single-wall, double-wall carbon nanotubes, or multi-wall carbonnanotubes and combinations thereof. One of ordinary skill in the artwill recognize that many of the specific aspects of this inventionillustrated utilizing a particular type of carbon nanotube may bepracticed equivalently within the spirit and scope of the disclosureutilizing other types of carbon nanotubes.

Manufacture of Discrete Carbon Nanotubes of MOLECULAR REBAR

An illustrative process for producing discrete carbon nanotubes follows:3 liters of sulfuric acid (containing 97 percent sulfuric acid and 3percent water), and 1 liter of concentrated nitric acid (containing 70percent nitric acid and 30 percent water), are added into a 10 litertemperature controlled reaction vessel fitted with a sonicator andstirrer. 40 grams of non-discrete carbon nanotubes, grade Flowtube 9000from CNano corporation, are loaded into the reactor vessel whilestirring the acid mixture and the temperature maintained at 30° C. Thesonicator power is set at 130-150 watts and the reaction is continuedfor 3 hours. After 3 hours, the viscous solution is transferred to afilter with a 5 micron filter mesh and much of the acid mixture removedby filtering using a 100 psi pressure. The filter cake is washed onetime with about 4 liters of deionized water followed by 1 wash of about4 liters of ammonium hydroxide solution at pH greater than 9 and then 2more washes with 4 liters of deionized water. The resultant pH of thefinal wash is 4.5.

A small sample of the filter cake is dried in vacuum at 100° C. for 4hours and a thermo gravimetric analysis taken. The amount of oxidizedspecies on the fiber is 4 percent weight and the average aspect ratio asdetermined by scanning electron microscopy to be 60. The discrete carbonnanotubes (CNT) in wet form are added to water to form a concentrationby weight of 1 percent and the pH is adjusted to 9 using ammoniumhydroxide. Sodium dodecylbenzenesulfonic acid is added at aconcentration of 1.5 times the mass of oxidized carbon nanotubes. Thesolution is sonicated while stirring until the CNT are fully dispersedin the solution. Sufficient dispersion of individual tubes (discrete) isdefined when the UV absorption at 500 nm is above 1.2 absorption unitsfor a concentration of 2.5×10-5 g CNT/ml.

Functionalized carbon nanotubes of the present disclosure generallyrefer to the chemical modification of any of the carbon nanotube typesdescribed hereinabove. Such modifications can involve the nanotube ends,sidewalls, or both. Chemical modifications may include, but are notlimited to covalent bonding, ionic bonding, chemisorption,intercalation, surfactant interactions, polymer wrapping, cutting,solvation, and combinations thereof Use the functionalization agentsattached in some fashion chemically or mechanically to the MOLECULARREBAR or discrete carbon nanotubes are useful to disperse the MOLECULARREBAR in either the urethane component and/or the polyol component andto maintain the dispersion of the discrete carbon nanotubes duringsubsequent polymerization. Use of specific functionalization agentswhich can attach to the MOLECULAR REBAR in polyurethanes can react tothe polyurethane structure, either in the hard segment or the softsegment of the urethane, or both the hard and the soft segment of theurethane.

Materials comprising discrete carbon nanotubes can have other additivessuch as other fibers (carbon, graphite, polymeric (polypropylene,polyethylene to name just a couple), and particulates (such as powders(carbon black), sand, diatomaceous earth, cellulose, colloids,agglomerates, antimicrobials)).

Additives can be included and can further react or be completely inertwith other components of the formulation. Fibrous additives can besurface active to react with surroundings.

Individual discrete carbon nanotube fibers can have an aspect ratio offrom about 10 to about 500, preferably 25-200 and most preferably50-120. The aspect ratio of the discrete carbon nanotube fibersgenerally does not change significantly after processing into theend-use application. For example, the aspect ratio may change or reduceonly a certain percentage of the original aspect ratio. Preventing theaspect ratio from significantly changing in discrete carbon nanotubes orMOLECULAR REBAR is important to prevent the MOLECULAR REBAR frombecoming less effective for mechanical property improvements in thefinal end-use application. Polyurethane applications and dispersionsespecially benefit from a small aspect ratio change when forming thedispersion.

Generally, the aspect ratio in the final polyurethane containing mixtureis at least about 50% to about 99% of the aspect ratio of the startingnanotube fibers. The lower range of the aspect ratio retention can be60%, 70%, 80%, or 90%. Preferably the lower range of the aspect ratioretention is about 95% or greater than the original aspect ratio of thestarting nanotube fibers. The higher range of the aspect ratio retentionis 100% or less, 99% or less, 97% or less, 90% or less, 85% or less, or75% or less. The preferred range of aspect retention ratio is from about80% to about 99%. For example, if the aspect ratio, on average, is about100, then the aspect ratio retention ratio preferably is from about 80%to about 99% of 100. That is, after processing into the fabricatorarticle (or dispersion), the aspect ratio is about 80 to about 99.Similarly in another example, the aspect ratio retention for beginningaspect ratio of 200 would be about 160 to about 198. The lower end andthe higher-end range of the aspect ratio retention as described hereincan be mixed in any amount. That is the aspect ratio retention can be60% to a high range of 75%. Or the aspect ratio retention can be 60% toa high range of 85%. Or the aspect ratio retention can be 60% to a highrange of 99%. Similar ranges and combinations apply for various limitsof the high and low ranges

The discrete carbon nanotube fibers MOLECULAR REBAR (MR) can comprise0.1 to 20% by weight of the formulation, preferably 0.2 to 10, morepreferably 0.25 to 5% by weight of the formulation.

The discrete carbon nanotube fibers can all be about the same aspectratio (length to diameter ratio) of +/− 10%, for example L/D from 90 to110, or for another example L/D from 225 to 275; having uniform L/D isuseful for evenly distributing load across a shaped article.

Based on application (such as reinforcing foam articles), 10% by weightor less of the discrete carbon nanotubes MR of the formulation cancomprise L/D of about 100 to 200 and about 30% or more of the discretecarbon nanotubes MR of the formulation can comprise L/D of 40 to 80.

An additional embodiment of this invention comprises a compositionincluding a plurality of discrete carbon nanotube fibers, said fibershaving an aspect ratio of from about 10 to about 500, and wherein atleast a portion of the discrete carbon nanotube fibers are open ended,preferably wherein 40% to 90% by number of the carbon nanotubes have anaspect ratio of 30-70, and more preferably aspect ratio of 40-60, and 1%to 30% by number of aspect ratio 80-140, most preferably an aspect ratioof 90 to 120. In statistics, a bimodal distribution is a continuousprobability distribution with two different modes. These appear asdistinct peaks (local maxima) in the probability density function. Moregenerally, a multimodal distribution is a continuous probabilitydistribution with two or more modes. The discrete carbon nanotubes canhave a unimodal, bimodal or multimodal distribution of diameters and/orlengths. For example, the discrete carbon nanotubes can have a bimodaldistribution of diameters wherein one of the peak values of diameter isin the range 1 to 7nanometers and the other peak value is in the range10 to 40 nanometers. Likewise, the lengths of the discrete carbonnanotubes can have a bimodal distribution such that one peak has amaximum value in the range of 150 to 800 nanometers and the second peakhas a maximum value in the range 1000to 3000 nanometers. Using specificaspect ratio distinct carbon nanotubes, or MOLECULAR REBAR, incompositions such as polyurethane, can have beneficial effects. Theseeffects include more complete filling of interstitial voids in a finalcomposition at a given volume fraction of carbon nanotube fibers, wherecarbon nanotubes fibers having a uniform L/D (aspect ratio) can leaveunfilled areas devoid of fibers—leading to poorer mechanicalreinforcement performance. Varying the aspect ratio, including use ofspecific modalities of aspect ratio, can provide an improved balance ofrheology and uniform reinforcement of compositions, such as polyurethanecompositions of the invention.

A further embodiment of this invention comprises discrete carbonnanotubes fibers, said fibers further comprising a blend of fibershaving different functionality or different amounts of the samefunctionality. The weight ratio of the blend of fibers of differentfunctionalities, or with different levels of the same functionality, canrange from about 95/5 to 50/50, preferably range about 75/25 to 50/50.Specifically, 50 to 95 percent of the discrete carbon nanotube fiberscan have a functionality attached to a level averaging at one level;(for example 10% by weight of the carbon nanotube fiber) where 5-50percent of the discrete carbon nanotubes have a relative functionalitylevel different from that of the first group by at least 10%. Thesefunctionalities can be the same or similar functionalities, or they canbe entirely different Functionalities—depending on the end useapplication. The blend components of functionalized fibers may alsocontain specific modalities of aspect ratio. This includes placingfunctionality (e.g., 0.5 to 4%, on average 2%, weight of the functionalgroups on the carbon nanotube fibers) on discrete carbon nanotube fibershaving a certain aspect ratio (such as relatively high L/D from about300-600) and another level of (e.g., from 10% to 50%, on average 25%weight of the functional groups on the carbon nanotube fiber), thefunctionality being the same or different functionality on discretecarbon nanotubes having L/D from 60-120.

It is preferable for the discrete carbon nanotubes of the invention tocomprise the functionalization; however non-discrete carbon nanotubefibers (such as that as originally made and consequently stillentangled)—whether intentionally added to the compositions, or whethernot made discrete and/or not functionalized—can be included in thecompositions herein.

Any of the aspects disclosed in this invention with discrete carbonnanotubes may also be modified within the spirit and scope of thedisclosure to substitute other tubular nanostructures, including, forexample, inorganic or mineral nanotubes. Inorganic or mineral nanotubesinclude, for example, silicon nanotubes, boron nitride nanotubes andcarbon nanotubes having heteroatom substitution in the nanotubestructure. The nanotubes may include or be associated with organic orinorganic elements such as, for example, carbon, silicon, boron andnitrogen. Association may be on the interior or exterior of theinorganic or mineral nanotubes via Van der Waals, ionic or covalentbonding to the nanotube surfaces.

The flexural strength or resistance to cracking of the compositions canbe determined by flexural bending of the composition on a thin aluminumor copper film in a 3-point bending fixture and an Instron TensileTesting machine. The test is analogous to standard test procedures givenin ASTM D-790. The stress to crack the composition through the thicknessis recorded. Units are in MPa.

The adhesive strength of the compositions can be determined by using lapshear strength procedures and the Instron Tensile Testing Machine. Thetest is analogous to EN 1465. The specimen consists of two rigidsubstrates, for example aluminum sheets or copper sheets, bondedtogether by the composition in a lapped joint. This causes the two endsof the specimen to be offset from the vertical load line of the test.The composition is placed between two strip of material. The stress tofailure on pulling the lapped specimen is recorded. Units are in MPa.The improvement in flow processibility of the compositions can bedetermined using a rheometer, for example, utilizing concentriccylinders with a well-defined geometry to measure a fluid's resistanceto flow and determine its viscous behavior. While relative rotation ofthe outer cylinder causes the composition to flow, its resistance todeformation imposes a shear stress on the inner wall of the cup,measured in units of Pa. At a certain shear stress, micro fracture ofthe composition can occur resulting in poor homogeneity.

Fabricated articles which can be usefully made with the inventioninclude foams, both hard and soft, molded articles in general, includingblow molded, injection molded, and other thermally formed moldedarticles. Dispersion's comprising the inventive compositions can also beformed. These dispersions can include plans with other materials. Or thedispersions of the invention can be used by themselves.

Using dispersed MOLECULAR REBAR in polyurethanes can improve manydifferent physical properties, such as modulus, strength, fatigueproperties, melt strength, coefficient of expansion, low temperatureproperties, static and conductive properties, and insulation properties.Insulation properties can be enhanced by incorporating MOLECULAR REBARdue to radiation absorption.

Using MOLECULAR REBAR in polyurethanes can improve physical propertiesof foams, including minimizing sidewall breakage because of the uniquesize and aspect ratio of MOLECULAR REBAR unlike most other materials.

Another embodiment of this invention comprises discrete carbon nanotubesfibers that have a sufficient number of defects within the wall or wallsof the discrete carbon nanotube fibers such that they are allowed tocurl and uncurl during at least one of the steps of forming apolyurethane. An example of defects that facilitate bending or curlingalong the length of the carbon nanotubes are Stone-Wales defects, whichare the rearrangement of the six-membered rings of graphene intoheptagon-pentagon pairs that fit within the hexagonal lattice of fusedbenzene rings constituting a wall of the carbon nanotubes.

Stone-Wales defects are thought to be more prevalent at the end capsthat allow higher degrees of curvature of the walls of carbon nanotubes.During oxidation the ends of the carbon nanotubes can be opened and alsoresult in higher degrees of oxidation than along the walls. The higherdegree of oxidation and hence higher polarity or hydrogen bonding at theends of the tubes are thought useful to help increase the averagecontour length to end to end distance ratio where the tubes are presentin less polar media such as natural rubber, cis-butadiene, styrenebutadiene, isoprene, polystyrene, acrylonitrile butadiene. The ratio ofthe contour length to end to end distance can be advantageouslycontrolled by the degree of thermodynamic interaction between the tubesand the medium. Surfactants can be usefully employed also to modify thethermodynamic interactions between the tubes and the medium of choice.

A ratio of the average contour length to end to end distance greaterthan about 1.2 is advantageous to reduce the viscosity of the mixture ofpolyol and/or isocyanate containing discrete carbon nanotube fibers,relative to the same weight fraction of discrete carbon nanotubes thathave average contour length to end to end distance in the range 1 to1.1. The reduced viscosity is advantageous for improved mixing of thecomponents and fabrication into fibers, foams or films, particularlywhere the product also requires impregnation of the polyurethanecontaining discrete carbon nanotube fibers into fiber matts, such asglass fiber matts or aramid fiber matts (KEVLAR or NOMEX, from Du Pont)for further reinforcement of mechanical properties. The ability for thediscrete carbon nanotube fiber to uncurl to some degree is particularlyadvantageous for foams where the discrete carbon nanotubes are expectedto fit within the cell wall or strut without causing premature ruptureof the cell wall or strut. As the foam cell is growing there isorientation of the material which enables the discrete carbon nanotubefibers with defects to reduce the ratio of the average contour length toend to end distance. The reduction of the ratio of the average contourlength to end to end distance by orientation or dilution in the mediumis at least 10% or more, preferably at least 20% or more, and mostpreferably 50% or more.

Crystallization Enhancement

By forming discrete carbon nanotubes known as MOLECULAR REBAR, and theiraddition in materials, crystallization enhancement has been observed forvarious polymers and polymer components. This enhanced crystallizationis very beneficial for forming higher rigidity materials and morecrystalline structures including what are essentially noncrystallinematerials. These essentially noncrystalline materials include syntheticand natural rubber. Crystallization enhancement for essentiallynon-crystalline materials (less than about 2% by weight crystallinity asdetermined by differential scanning calorimetry or x ray diffraction),or essentially amorphous materials, such as rubber, is useful toincrease their thermo-mechanical properties or strength of resultingcompositions. These compositions can include other additives such ascarbon black or silica for reinforcement. By forming crystals, even insmall amounts, the useful temperature range for resulting compositionsis increased. So for example, a natural rubber enhanced with discretecarbon nanotubes or MOLECULAR REBAR has an elevated useful temperaturerange higher than that for the same natural rubber modified withnon-discrete carbon nanotubes (“bird nests” or agglomerations). Similarbehavior for other polymers and materials is useful by incorporatingdiscrete carbon nanotubes or MOLECULAR REBAR.

Typical amorphous or non-crystalline polymers do not have a meltingpoint, but rather a melting range. By incorporating MOLECULAR REBAR(discrete carbon nanotubes), crystals can be formed in an otherwiseamorphous polymer. These crystals are then “tied” to each other by theinterconnectivity of the MOLECULAR REBAR, acting to reinforce andenhance the mechanical and thermal properties. MOLECULAR REBAR acts as atype of nucleating agent, but it does more, since the matrix is nowreinforced with molecular level carbon nanotubes. Typical propertyenhancements are at least 10 percent higher than the same propertywithout incorporating MOLECULAR REBAR. However, these propertyimprovements are usually much higher than 10 percent, and can range toas much as 100percent improvement, or more.

Semi-crystalline polymers also benefit from addition of MOLECULAR REBAR.Incorporating discrete carbon nanotubes can increase the crystalformation of the resultant thermally formed polymer. Such thermalforming can depend on various factors, but typically the polymer orpolymer blend containing the MOLECULAR REBAR is heated to form into apart, and then cooled. Cooling can take place gradually, or cooling canbe controlled at certain temperatures per minute. Rapid quench can alsobe employed, and the resultant crystal size, and even content, maydepend on the cooling degree and cooling rate. Generally, rapid quenchresults in smaller crystals while slow, gradual quench conditions allowlarger crystal growth. Incorporating MOLECULAR REBAR, at varyingconcentration or aspect ratios (or distributions of aspect ratios) hasnow been found to influence crystal formation and tie moleculeinterconnectivity. MOLECULAR REBAR in polymers, such as semi-crystallinepolymers, interacts with the polymer molecules, resulting in strongerand tougher polymer compositions.

For both amorphous and semi-crystalline polymers, on addition ofMOLECULAR REBAR the degree of crystallinity can increase by as little as1 percent, or can go up to as much as 75 percent compared to the samepolymer with no MOLECULAR REBAR. Typical increase in crystallinity isfrom about 1 percent to about 50 percent, preferably from about 1percentto about 40 percent, more preferably from about 1 percent to about 30percent, and especially from about 1 percent to about 20 percent. Allpercents described with respect to crystallinity are based on weightpercent of the selected polymer. Crystallinity is typically measuredfrom the endotherm of a thermogram obtained by differential scanningcalorimetry, but can also be determined by X-ray spectroscopy.

Semi-crystalline polymers which can be modified by incorporatingMOLECULAR REBAR include polyethylene such as single site polymers, forexample EXACT (Exxon), AFFINITY and ENGAGE (Dow), Ziegler-Natta polymers(DOWLEX by Dow, and FLEXOMER by Union Carbide— now Dow) and highpressure, free radical low density polyethylene (LDPE). Bothpolyethylene and polypropylene polymers can include various copolymersof ethylene or propylene and at least one alpha-olefin (such as hexene,butane, propene, octene) and combinations of comonomers (terpolymers forinstance)). Examples of propylene copolymers include VERSIFY (Dow).Homopolymers (ethylene and propylene) can also benefit from addition ofdiscrete carbon nanotubes. Other types of ethylene polymers includeELITE (Dow) and INFUSE olefin block copolymers ((Dow).

Other polymers and copolymers can also utilize MOLECULAR REBAR andincluding, but not limited to, ethylene/acrylic acid copolymers, such asPRIMACOR (Dow) and VISTAMAXX (Exxon) and NUCREL (DuPont) (and ionomersmade therefrom such as SURLYN (DuPont)), polyethers, polyesters,fluorinated polymers, and polyamides.

Blends of polymers disclosed herein can also be employed using theMOLECULAR REBAR to aid crystallization. Such polymer blends are notmerely limited to those recited herein, but can include others, to theextent the ultimate polymer blend can still be processed and useful.

What is claimed is:
 1. A composition comprising the reaction product ofat least one urethane based polymer or pre-polymer and at least aportion of discrete oxidized multiwall carbon nanotubes having anoriginal aspect ratio of from about 10 to about 500 wherein the retainedaspect ratio of the discrete oxidized carbon nanotubes in the reactionproduct is at least about 60% or greater of the original aspect ratio.2. A composition comprising the reaction product of at least oneurethane based polymer or pre-polymer and at least a portion of discreteoxidized multiwall carbon nanotubes having an original aspect ratio offrom about 10 to about 500, wherein the urethane based polymer orprepolymer comprises at least one polyol and/or at least one isocyanate,and wherein the discrete oxidized carbon nanotubes are polymerized withthe urethane polymer or pre-polymer and wherein the retained aspectratio of the discrete oxidized carbon nanotubes in the reaction productis at least about 60% or greater of the original aspect ratio.
 3. Thecomposition of claim 2 wherein the urethane based polymer or pre-polymercomprises at least one polyol.
 4. The composition of claim 2 wherein theisocyanate comprises aromatic or aliphatic groups.
 5. A cementcomprising discrete oxidized multiwall carbon nanotubes having anoriginal aspect ratio of from about 10 to about 500 wherein the retainedaspect ratio of the discrete oxidized carbon nanotubes in the cement isat least about 60% or greater of the original aspect ratio, wherein thecement has improved crack resistance as determined by flexural bendingof the composition on a thin aluminum or copper film in a 3-pointbending fixture and an Instron Tensile Testing machine.
 6. A cementcomprising discrete oxidized multiwall carbon nanotubes having anoriginal aspect ratio of from about 10 to about 500 wherein the retainedaspect ratio of the discrete oxidized carbon nanotubes in the cement isat least about 60% or greater of the original aspect ratio.
 7. A mortarcomprising the cement of claim 6 for use with cement blocks and rocks,wherein the mortar resists cracking and crumbling to insure longer lifecompared to a mortar without discrete oxidized carbon nanotubes.
 8. Thecomposition of claim 1 where the portion of discrete oxidized carbonnanotubes are open ended.
 9. The composition of claim 1 furthercomprising at least one polymer other than the at least one urethanebased polymer or prepolymer.
 10. The composition of claim 1 wherein theportion of discrete oxidized carbon nanotubes are furtherfunctionalized.
 11. The composition of claim 1 wherein the discreteoxidized carbon nanotubes have a residual metals level of less thanabout 4% by weight of the carbon nanotubes.
 12. The composition of claim9 wherein the at least one polymer other than the at least one urethanebased polymer or prepolymer is selected from the group consisting ofvinyl polymers; fluorinated polymers; conductive polymers; polymersderived from natural sources; and cellulosic based materials;polyethers; polyesters; and polyamides, either as graft, block or randomcopolymers; and mixtures thereof.
 13. The composition of claim 1 whereinthe discrete oxidized carbon nanotubes comprise from about 0.1 to about90 weight percent of the composition.
 14. The composition of claim 1 inthe form of free flowing particles.
 15. The composition of claim 1comprising additional inorganic structures.
 16. The composition of claim15 wherein the additional inorganic structures comprise elementsselected from the groups two through fourteen of the Periodic Table ofElements.
 17. The composition of claim 15 wherein the additionalinorganic structures are selected from the group consisting of silver,gold, silicon, vanadium, titanium, chromium, iron, manganese, tin,nickel, palladium, platinum, cobalt, aluminum, gallium, germanium,indium, antimony, copper and zinc, cadmium, mercury, and mixturesthereof including oxides and other derivatives.
 18. The composition ofclaim 15 wherein the additional inorganic structures comprise non-fibercarbon structures.
 19. The composition of claim 18 wherein the non-fibercarbon structures comprise components selected from the group consistingof carbon black, graphite, graphene, oxidized graphene, fullerenes andmixtures thereof.
 20. The composition of claim 1 wherein the retainedaspect ratio of the discrete oxidized carbon nanotubes in the reactionproduct is at least about 90% or greater of the original aspect ratio.21. The composition of claim 2 wherein the retained aspect ratio of thediscrete oxidized multiwall carbon nanotubes in the reaction product isat least about 90% or greater of the original aspect ratio.
 22. Thecement of claim 5 wherein the retained aspect ratio of the discreteoxidized multiwall carbon nanotubes in the cement is at least about 90%or greater of the original aspect ratio.
 23. The cement of claim 6wherein the retained aspect ratio of the discrete oxidized multiwallcarbon nanotubes in the cement is at least about 90% or greater of theoriginal aspect ratio.